1. Field
The present disclosure relates to an anode active material including a multilayer metal nanotube, an anode and a lithium battery including the anode active material, and methods of preparing the anode active material.
2. Description of the Related Art
A representative example of an anode material for a lithium battery is a carbonaceous material such as graphite. Graphite has excellent capacity retention characteristics and voltage characteristics, and the volume of graphite changes minimally during intercalation or deintercalation of lithium. Thus, the stability of a battery including graphite is high. A theoretical capacity of graphite is about 372 millampere-hours per gram (mAh/g) and an irreversible capacity thereof is high.
Metals alloyable with lithium may be used as anode active materials for lithium batteries. Examples of metals alloyable with lithium are silicon (Si), tin (Sn), and aluminum (Al). Metals alloyable with lithium have a large capacity. For example, Si has a capacity 10 times greater than that of graphite. However, the metals alloyable with lithium expand or contract during charging or discharging, thereby isolating an active material in an electrode, and such metals can promote electrolyte decomposition, due to the increased specific surface area.
To reduce the volume expansion of the metals alloyable with lithium and address electrolyte decomposition, the metals alloyable with lithium may be prepared as nano-size structures. For example, a silicon nanotube used as an anode active material is disclosed by Park et al. in Nano Letters, 2009, 9, pp. 3844-3847. However, while the silicon nanotube has high capacity retention characteristics, its high-rate characteristics are poor.
Thus there remains a need for a high capacity anode active material with improved capacity retention characteristics and high-rate capability.